Heat recovery and washing system for sulphite pulp



Oct. 30, 1934. J D. JENSSEN 1,978,749

HEAT RECOVERY AND WASHING SYSTEM FOR SULPHITE PULP Oct. 30, 1934.

J. D. JENSSEN HEAT RECOVERY ND WASHING SYSTEM FOR SULPHITE PULP Filed June 8. 1933 2 Sheets-Sheet F- l G 41.

Patented Oct. 30, 1934 t l 1 UNITED STATES PATENT oFFlcE HEAT RECOVERY AND WASHING SYSTEM FOR SULPHITEl PULP Jacob Darre Jenssen, ew York, N. Y., assigner to G. D. Jenssen Company, New York, N. Y.

Application June 8, 1933, Serial No. 674,799 17 Claims. (Cl. 92-11) 'Ihe invention relates to a heat, recovery and The making of the acid liquor does not differ Washing system for sulphite pulp, as described so greatly from some of the best known methods in the present specication and illustrated in the except in so far as the main feature of this accompanying drawings that form part of the invention is made use of in materially speeding 5 same. I up the manufacture and strengthening the liquor, so The invention consists essentially in distributso in referring to the drawings, the sulphur diing the heat from the steam generated to cook oxide gas pipe, indicated by the numeral 15 which the wood throughout the plant, in order to mainleads from a sulphur burning tank empties into tain temperatures at a minimum consumption the casing of a gas fan, indicated by the nu- 10 of fuel and to produce pulp free from blemishes meral 16, being drawn into said fan and delivered 65 due to uneven temperatures and also to recover to the tower 17, known as the strong acid tower, gas, as pointed out in the claims for novelty at the inlet 18 towards the lower end. following a description in detail of the operation. This delivery is below the acid producing ma- The objects of the invention are to facilitate terial in thetower (not shown), but which may t the treatment and manufacture of the acid liquor be limerock or other substance. 7p, and to accumulate recovered liquor centrally for The water or weak acid liquor enters the tower use in the digester and coincidently with the at the inlet 19, near to the upper end and the manufacture, delivery, accumulation of the acid pipe 20 extends from the pump 21 to said inlet liquor and the cooking of the pulp, distribute 19 and through the wall of the tower. the heat throughout the system, and in this way The outlet 22 to the atmosphere may be used 75 increase the output and improve the product as to clear the tower and is closed by the cap 23 well as speeding up both the making of the acid in operating the tower 17 with the Weak acid liquor and the nishing of the pulp; to eiect tower 24. economy by reducing the consumption of fuel 'Ihe outlet near the upper end 25 of the tower to the accumulation of recovered acid liquor, in towards the lower end of the weak acid tower fact todo in regard to the release of the heat 24, and the limerock or other material for proand gas, what is at present not considered pos ducing the acid in the tower 24 (not shown) sible, byvreducing the pressure at the start of is above the inlet 27. The vent 28 to the atmosrelease below the one which is necessary in order phere releases the spent gas. 85 to b e able to empty the digester; to furnish a The water inlet 29 is connected by the pipe 30 sufficient amount of hot water for the initial to the pump 31 and the acid liquor outlet 32 is vwashing of the pulp reclaimed from the heat connected by the pipe 33 to the pump 21. of the liquor in the digester, and at all times 'I'he water supply pipe 34 is connected to the to maintain the water at a high enough tempump 31 which pumps the water up to the top 90 perature for washing purposes, so that it will of the tower 24, thus when the system is in full not be necessary to wash the pulp in cold water, operation, the inlet 19 receives only weak acid as it is a well known fact that washing with liquor back from the tower 24, but in starting, hot water is much to be preferred, and generally naturally the water can be pumped up to the to distribute the hot water throughout the system inlet 19 by the pump 21. 95 where it will do the most good Without interfer- The pipe 35 leads from the steam pipe 36 to ing with the emciency of the digester and in the reservoir of the pump 21 and this steam pipe all'respects so arrange the conditions as to prothrough the valve 37 and pipe 38 is connected duce the best and quickest results. to the pump 39, andthis pump is connected by In the drawings, Figure 1 is an elevational the other section of this pipe 38 to the hot water 10o view partly in section showing the digester, tank 40. washer and contiguous parts, in the complete 'Ihe strong acid tower and the weak acid tower plant. work together in producing the acid liquor. The Figure 2 is a plan view of the plant. water comes from its source to the pipe 34 and 3 Figure 3 is an enlarged sectional view of the enters the tower 24 at the upper end and as usual 105 digester and circulation passages in the vicinity trickles down through the limerock, while the thereOf. gas received from the tower 17 rises and meets Figure 4 is an enlarged view of the acid liquor this water and produces the weak acid liquor, towers-broken away and the tanks and connecthis weak acid liquor flowing outwardly through tions associated therewith. the outlet 32 and pipe 33 to the reservoir of the 110 in the generation of steam and materially add 17 1s connected by the pipe 26 to the inlet 27 80 y is controlled by 4 through the outlet 67,

2 pump 21, this pump being driven drives the weak acid liquor into and through the pipe and this weak acid liquor enters the strong acid tower at 19 and trickles down through the rock to the outlet 41 and from this outlet it flows through the pipe 42 to the pump 43.

It may be mentioned that the pump 21 receives during the operation of the system, water from the hot water tank and this water is pumped by to the reservoir of the pump heats the weak acid liquor in the pump reservoir 2l and is pumped up by the pump 21 with the weak acid liquor, thereby producing at the outlet 4l a strong working acid liquor.

The pump 43 pumps the raw acid liquor through the pipe 44 to the heat exchanger 45 from which it flows into and through the pipe 46 to the acid storage tank 47.

The pipe 48 from 16 is tapped by the pipe 49 communicating the suction side of the fan with the acid storage tank 47 thereby providing a vent` for the fan without losing any sulphur dioxide gas.

The heat exchanger is also connected sofar as the water is concerned by the pipe 50 to the water tank 51 thereby driving the water from the hot water tank 40, and this tank 51 is connected to the pump 52 through the valve 53 and this pump forces the water into and through the pipe 54.

The outlet 55 from the acid storage tank 47 is connected by the pipe 56 through the valve 57 to the Y connection having one outlet connected f to the pump 58 and the other'through the valve 59 to the acid liquor accumulator 60 through the inlet 61 at the lower end and this pump is also connected to the acid liquor supplypipe 62, which leads through the valve 63 to the digester 64 at the liquor inlet 65 at the lower end of said digester.

The digester is packed full of chips and these chips of course are affected by the acid liquor in the presence of heat.

The closing of the valve 63 and of course the valve v66 leaves only one outlet passage 67 which the valve 68, and the pump 69 beyond the valve 68 when the latter is opened, pumps the liquor into the heater 70, which is connected to the steam supply 98, and the valve 71 controls the port to the heater on the top side, and when this is opened the liquor may flow through the pipe 72 to the inlet 73 towards the upper end of the digester, and this circulation of hot acid liquor cooks the pulp which is eventually emptied as brown stock through the open valve 66 into the discharge receptacle 74.

The stock in this receptacle 74 is forced by the pump 75 through the pipe 76 and into the succession of washers described as the Aopener 77, the knotter 78 and the vacuum washer 79, flowing from these receptacles to the brown stock tank 80 to be forced by the pump 8l to the screens.

The water from the tank 51 is connected through the pipe 54 and valves 82 and 83 to the pipe.72, and this water is used for the first washing of the pulp after cooking, which is done within the digester with the valves 68 and 71 closed following the draining off of the acid liquor the valve 68, the valve 98 and heat exchange device to the sewer pipe 99.

The water is shut olf from the digester by the valve 84 and the valve 71 opened for the next operation and the valve 83 closed.

The circulating water continues to flow in from the feed pipe 86 into the heat exchanger 85 and flows up the pipe 87 to and through the open valve 88 into the pipe 89 and the hot water tank 40, but previously the valve 100 has been opened to assist in the flushing or washing performed in the digester, but this valve is now closed.

It may be mentioned that as soon as the short course of water through the pipe 87 and the pipe 54 and open valve 83 has been established, the valve 82 is closed so that only the first flushed water comes from the hot water tank 40, consequently there is no hesitation or pause in the operation due to the closing off of the heater 70 and of the draining of the digester 64.

The valve 90 is introduced in the pipe 91, which is connected to the accumulator 60 towards the lower end at the inlet 92, While the pipe 93 having the valve 94 introduced therein is connected to the jet condenser 95 and this jet condenser is connected by the pipe 96 to the acid liquor feed pipe 62 through the valve 97, and by the pipe 101 to the top of the accumulator communicating by that pipe with the interior of the accumulator.

The valve 90 is opened several times during the cooking so as to relieve the apparatus of the high pressure during the operation, and this relieves the digester of gases from the acid liquor, which reach the accumulator at the inlet 92 and add to theaccumulation of acid liquor.

The valve 94 is opened at the end of the cooking and the gas escapes, and this is heavily laden with water and flows along the low pressure relief pipe to the jet condenser Where the liquid portion of it drops down through the top of the accumulator while any gas left from it flows down the pipe 96 to the feed.

In the event of the circulation in the digester being in an .opposite direction than that shown, which is from the bottom to the top, then the wash water will be admitted at the bottom of the digester and the liquor taken out at the top, and insead of using a jet condenser as shown, another type of condenser may be used.

At present the digesters are emptied by opening the discharge valve, when the digesters are under pressure, and consequently all the heat and also a certain amount of sulphur dioxide gas still contained in the liquor are going to waste.

The purpose of this method is to reclaim a large portion of this heat and gas.-

The hot water in the tank is shown as being used for heating Water for acid making, heating the raw acid from the acid system and for heating pulp, but can also be used for other purposes. When used for heating pulp, the water is taken from the steam pipe 36. A

It will now be seen that the system throughout is particularly the distribution of the heat throughout the system from the same source,

namely from the Steam Supply, and this does everything in the way of concentrating the heat at certain points where it is most needed, also the accumulator forms an extremely important feature in the recovery of acid liquor through'the l* returning to the system of steam and gas ordinarily freely discharged.

What I claim isz- 1. In a heat, recovery and washing systemfor sulphite pulp, an acid liquor making apparatus, a digester for cooking the wood, a source of heat connected to said digester and distributed in various connections from said apparatus to said digester and means said digester.

for circulating acid liquor in 2. In a heat, recovery and washing system for sulphite pulp, an acid liquor making apparatus, a digester for cooking the wood, a source of heat connected to said digester, an acid liquor accumulator adapted to collect; from the digester recovered acid liquor and means for circulating acid liquor in said digester.

3. In a heat, recovery and washing system forV sulphite pulp, an acid liquor making apparatus, a digester having inlet and outlet openings at top and bottom and high and low pressure relief passages from the upper end and a circulating passage for acid liquor adapted to form a subsequent Water passage, a source of heat connected to said digester and distributed in various connections from said apparatus to said digester and means for circulating acid liquor in said digester.

4. In a heat, recovery and washng system for sulphite pulp, an acid liquor making apparatus having a strong acid tower connected to a hot water supply and to a weak acid liquor supply, a digester for cooking the wood, a source of heat connected to said digester and distributed in various connections from said apparatus to said digester and means for circulating acid liquor in said digester.

5. In a heat, recovery and washing system for sulphite pulp, an acid liquor making apparatus having a weak acid tower and a strong acid tower connected respectively to an outside water supply and to a hot water tank and to one another and finally discharging from the fstrong acid tower, a digester connected to the discharge and charged with wood, a, source of heat connected to said digester and distributed in various connections from said apparatus to said digester and means for circulating acid liquor in said digester. l

6. A heat, recovery and washing system for sulphite pulp comprising a steam feed pipe connected to a suitable source of supply, a water feed pipe from a suitable source, acid liquor making apparatus and digester connected thereto and connecting ,tubular passages including heat exchange devices for distributing said liquor water andsteam throughout the system.

. 7. A heat,-recovery and washing system, for sulphite pulp, comprising a steam feed pipe con- -nected to a suitable source of supply, a water feed pipe from 'a suitable source, acid liquor v making apparatus and digester connected thereto, an acid liquor accumulator receiving recovered acid liquor from said digester-and delivering acid liquor thereto and connecting tubular passages and Water,receptacles including heat exchange devices for distributing said liquor water and steam throughout the system.

8. A heat, recovery and washing system for sulphite pulp, comprising a steam feed pipe connected to a suitable source of supply, a water feed pipe from a suitable source, acid liquor making apparatus including a sulphur dioxide gas feed, towers and hot water tank having tubular connections and force pumps bringing the liquor to strength and discharging it to a storage tank, tubular passages and water receptacles including said hot water tank, heat exchange devices distributed throughout said passages, a digester connectedfto said acid liquor 3 for cooking and to heated water for washing purposes, and a washing device beyond the discharge of the digester.

9. A heat, recovery and washing system for sulphite pulp, comprising a steam feed pipe connected to asuitable source of supply, a water feed pipe from a suitable source, an acid liquor making apparatus including a hot water tank and a storage tank for the acid liquor, a digester connected to said storage tank and having an accompanying outside passage for circulating liquor from bottom to top and return, means for cutting out the lower portion of said passage and substituting water in the upper portion for the first washing and means for washing the pulp beyond the final discharge of the pulp from the digester.

10;A heat, recovery and washing system for sulphite pulp, comprising a steam feed pipe connected to a suitable source of supply, a water feed pipe from a suitable source, an acid liquor making apparatus including Weak and strong acid liquor towers having a sulphur dioxide gas connection to the strong acid tower with an exhaust gas connection to the weak acid tower and a water connection to the weak acid tower and weak and hot water connection to the strong acid tower, the latter having a discharge leading to the liquor'storage tank and the former discharging to be lifted to the strong acid tower and an accumulator for liquor and a digester connected to the various parts and particularly to said storage tank.

11. A heat, recovery and washing system for sulphite pulp, comprising a steam feed pipe connected to a suitable source of supply, a water feed pipe from a suitable source, means for feeding acid liquor, a digester having a liquor opening at the bottom, a circulation opening towards the top and relief opening at the top, a walled passage from said bottom opening to said circulation opening and containing a heater section, a pump, valves and an upper section forming a liquor passage in cooking operations and a water passage in washing, and a vessel for receiving acid liquor recovered from said digester through said relief opening.

12. A heat, recovery and washing system for sulphite pulp comprising a steam feed pipe connected to a suitable source of supply, a water feed pipe from a suitable source, a digester having a heated circulation liquor passage adapted to form a water connection in cooperation therewith and relief openings at the top end, an accumulator connected to said relief openings directly and indirectly through a jet condenser and means for heat exchange devices distributed throughout the Water circulation in the system, and means for making and feeding acid liquor to said digester.

13. A heat, recovery and washing system for sulphite pulp comprising a steam feed pipe connected to a suitable source of supply, a water feed pipe from a suitable source, a digester having a heated and accompanying circulation passage for liquor, said passage forming an inlet for heated water for washing purposes, and high and low pressure valve controlled relief openings, an accumulator having an inlet towards the bottom and a top inlet respectively connected to said high and low pressure relief openings a jet condenser introduced in the low pressure connection, an outlet pipe from said accumulator to the feed pipe digester and to said condenser and intervening valves and pump and means for making acid liquor connected through a storage tank to said outlet pipe.

14. A heat, recovery and washing system for sulphite pulp comprising a steam feed pipe connected to a suitable source of supply, a water feed pipe from a suitable source, means for makving acid liquor connected through heat exchange devices to a feed mechanism, a digester having a circulation system and discharge opening and valves in the connection, means for washing the pulp within said digester connected through heat exchanges thereto, a series of washing receptacles beyond the discharge opening and a brown stock tank.

15. A system in producing sulphite pulp comprising the feeding of water coincidentls7 with the feeding of steam and the heating of the cooking acid liquor before and during the cooking of the Wood, the washing of the pulp with heated water before the pulp discharge and washing after the discharge.

16. A system in producing sulphite pulp corn- Lezama prising the feeding of Water coincidently with the feeding of steam, the introduction into Weak acid liquor of hot Water and bringing the diluted acid liquor into contact with an acid liquor forming gas and the transmitting of the acid liquor through a hot Zone to the digester and heating during cooking operations.

17. A system in producing sulphite pulp comprising the feeding of water coincidently with the feeding of steam, and the distributing of the heat by exchange throughout the acid liquor during the making and digesting and throughout the Water during the making of the acid liquor and the Washing of the pulp.

JACOB BARRE J ENSSEN, 

